Automatic gear shift



AUTOMATIC GEAR SHIFT Filed Sept. 22, 1957 2 Sheets-Sheet l I11 venfoz M afiwwe Feb.

F. FRIEDMAN AUTOMATIC GEAR SHIFT Filed Sept. 22, 1937 2 Sheets-Sheet 2 I is 22 ii m Patented Feb. 7, 19 39 I UNITED STATES PATENT OFFICE AUTOMATIG GEAR SHIFT Fabian Friedman, Watertown, Mass.

Application September 22, 1937, Serial No. 165,105

4 Claims.

My invention relates to automobiles or other self-propelled road vehicles in which means must be provided for transmitting power from the engine to the wheels through different gear ratios.

5 More specifically, my invention relates to an automatic gear-shifting apparatus wherein no clutch is necessary and the only manual control is a lever for engaging a reversing gear train.

Qne object of my invention is to provide a transmission wherein the shifting of the gears is governed solely by the speed of the engine. In the ordinary automobile, the driver must shift the gears whenever he sees fit, and unskillful drivers often seriously damage the automobile by shifting before the engine has attained sufficient speed or by failing to shift to a lower speed when the engine is laboring under a heavy strain,

as when the automobile is climbing a steep hill.

Moreover, in congestedcity traffic it often happens that confusion and delayresult when several automobiles which have been halted by a police ofiicer or trafiic signal attempt to start up again. Each driver picks his own time to shift, and the result is that traffic starts up in jerks instead of moving smoothly along at increasing speed. By providing automobiles with unconditionally automatic transmissions it is possible to avoid such disadvantages. In other words, traffic will move more smoothly when the human element is diminished in importance.

Another object of my invention is to prevent the damage to an automobile engine which results from racing the motor. It is the custom of persons ignorant of mechanics to race the engine as soon as it starts in order towarm it up for more efficient performance. This practice is to be avoided inasmuch as some parts of the engine heat up more rapidly than others and the consequent uneven expansion of the moving parts results in scarring of the cylinder walls and similar evils which shorten the life of the engine.

My invention comprises a gear slidably mounted on the drive shaft and adapted to be displaced through the operation of a centrifugal governor actuated by the drive shaft. As the speed of the latter shaft increases, the gear is pulled along the drive shaft to mesh successively with the forward speed gears connected to the driven shaft. The driven shaft has a universal jointwhich permits it to be moved sideways out of engagement with the forward speed gears and into engagement with a reversing gear mechanism. Movement of the driven shaft is effected by a lever extending into the body of the automobile near the seat of the'driver, and the only manual control of the gearing in the transmission is the lever which permits a change from forward speed to reverse.

Many attempts have been made to devise an automatic transmission, but no transmission known to me is unconditionally automatic in forward speeds and governed solely by the speed of the engine. The fact that my transmission functions in an unconditionally automatic manner necessarily results in the elimination of the disadvantages enumerated in the preceding paragraphs.

These and other features of my invention will be more readily understood and appreciated from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawings in which,-

Fig. 1 is a plan view of a transmission according to my invention with the cover removed for purposes of clarity,

Fig. 2 is a view in side elevation with the side wall removed,

Fig. 3 is a view in end elevation with several parts removed,

Fig. 4 is a view in cross section along the line IVIV in Fig. 1, and

Fig. 5 is a view in cross section of the drive shaft and centrifugal governor.

In carrying out my invention, I provide a rectangular box or casing l of cast iron or other suitable material, which is closed by a flat cover H bolted to the top thereof. Within the casing I0 is a transverse partition 13 containing bearings for the drive shaft l2 which is journaled horizontally in the casing l0. Adjacent the partition l3 (Fig. 2) on the shaft I2 is a collar 54 secured in a peripheral groove on the shaft I2. A helical compression spring I6 embraces the shaft l2 and abuts at one end against a stop ring l keyed to the collar M. A slip ring if on the shaft l2 abuts the other end of the spring l6 and is formed with four T shaped keys is which slide longitudinally along the shaft l2 in grooves. An external spur gear I9 is loosely fitted on the shaft I2, but is rigidly connected to the ring H and thus held against relative rotation with the shaft l2, although longitudinal move ment remains possible. A fly ball governor is dis posed on the shaft I2 and comprises four links 20 connected at equal intervals to the slip ring ll, four links 2| similarly connected to the collar 44, and four fly balls 22. Each of the links 20 is pivotally connected to one end of the links 2 I, and a fly ball is mounted on each one of the links 2| ad- 55 shaft 24 on which is keyed an elongated spur gear 25 which is constantly in mesh with the spur gear I9. Substantially below the gear 25 is a horizontal counter shaft 26 journaled in the end walls of the casing II], to which is keyed a gear 21 in mesh with the elongated gear 25.

Journaled in the end walls of the casing I6 in the side opposite the elongated gear 25 are three countershafts 28, 30, and 32 upon which are keyed gears 29, 3I, and 33. The latter gears, which are progressively smaller in diameter, are located adjacent the drive shaft I2 and in a space smaller in length than the length of the gear 25. Also keyed on the countershafts 28, 30, and 32 are gears 34, 35, and 36. The result is that each .countershaft has a gear at each end, and the gears on the same countershaft have the same diameter. The gears 34, 35, and 36 are normally meshed with :an elongated pinion gear 32 fixed to the driven shaft 38, which is journaled in the end wall of the casing II! in alignment with the drive shaft I2.

Adjacent the pinion 31 and on the same side of the casing I6 is a gear 49 keyed on a short horizontal shaft 39 journaled in the end wall of the casing I9 and the partition I3. A similarly journaled shaft M is disposed beneath the shaft 39 and carries a gear 42 which is meshed with the gear 40 and a gear 43 carried on the counter shaft 26. The gear 43 has the same diameter as that of the gear 21. o.

The driven shaft 38 is broken by a universal joint 44 and is so journaled in the end wall of the casing I 0 that slight lateral movement is possible. A forked lever 45 embraces the driven shaft 38 and is pivotally mounted on a boss 46 on the cover II.

In the operation of the structure described it must be assumed that the drive shaft I2 is suitably connected toan engine without the interposition of any clutch. .For the sake of convenience it will also be assumed that the shaft I2 rotates counterclockwise, or away from the observer. When the engine is started and before any considerable speed has been reached, the governor will be in the position shown in the drawings. The gear I 9 will rotate with the shaft I2 and turn the following train of gears: 25, 21, 43, 42, 49. If the lever 45 is manipulated so that the pinion gear 31" is held in mesh with the gear 49, it will be seen that the driven shaft .38 will be caused to rotate in clockwise direction counter to the direction of rotation of the drive shaft I2. The above described train of gears thus constitutes my reversing mechanism. If the gear .31 is maintained in mesh with the gear 49, it is out of mesh with the gears 34, 35, and 36, and if the speed of the engine is now increased, it will merely cause the driven shaft 38 to rotate faster,

Assuming that the engine is at idling speed and that the lever 45 has been moved to withdraw the pinion 31 from engagement with the gear 40 and place it in mesh with the gears 34, 35, and 36 (which is the situation in Fig. 1) the train of gears I9, 25, 21, 43, 42, 40, will be turning without a load. When the engine speed is increased, the centrifugal governor 22 will pull the gear I9 along the drive shaft I2 until it meshes withthe gear 29. The driven shaft 38 is then caused to rotate by the gear train I9, 29, 34, and 31. This is low, or first speed inasmuch as the diameter of the gears 29 and 34 is relatively large. A further increase in engine speed results in moving the gear I9 further along the shaft I2 until it is in mesh with the gear 3I which causes the driven shaft 38 to rotate by means of the gear train I9, 3|, 35, 31. This is the second speed, and the shaft 38 rotates more rapidly, inasmuch as the gears 3| and 35 are smaller than the gears 29 and 34. A further increase in speed moves the gear I 9 along the shaft I2 until it meshes with the gear 33 which causes the driven shaft 38 to rotate through the gear train I9, 33, 36, 31; This is high speed, and the gears 33 and 36 are considerably smaller than either the gears 29 and 34 or the gears BI and 35. Y

It will now be understood that the shifting of the gears is unconditionally automatic in forward speed. By properly spacing the gears 29, 3!, and 33 it is possible to predetermine the exact speeds at which shifting will take place. In other words, gear shifting can now be done by skilled machine designers instead of by unskilled automobile drivers. The speed of the engine controls the particular train ofgears to be used at any time.

The most important result of my invention is the fact that the gear ratio will always be the correct one for the speed of the engine.

Those skilled in the art will at once perceive many possible variations in the structure described and illustrated, but the scope of my invention is limited only by the appended claims.

I claim:

1. In a transmission having rotatably' mounted driving anddriven shafts, a sliding gear slidably keyed on .said driving shaft, a pinion on said driven shaft,- a centrifugal governor for sliding said gear to and fro according to the speed of the driving shaft, three countershafts, adjacent said driving shaft, aset of gears on said countershafts constantly engaged with said pinion, and a second .set of gears on said countershafts adapted to be successively engaged with said sliding gear, and reversing gears disposed between said driving and driven shafts.

2. An automatic transmission comprising a casing, driving anddriven shafts in said casing, a sliding gear on said driving shaft, a pinion on said driven shaft, centrifugal governor means on said driving shaft for moving said sliding gear,

three countershafts in .said casing, gears disposed on said counter-shafts and in mesh with said pinion, and transmission gears disposed within said casing on said three countershafts, the transmission gears on said three countershafts being successively meshed with said sliding gear as the engine speed increases or decreases.

3. Automatic power transmission system comprising a casing, driving and driven shafts, three forward speed countershafts geared to said driven shaft, a sliding gear on said driving shaft adapted successively to engage gears on said three countershafts, a reversing shaft having a gear thereon geared to said sliding gear, a second gear on said reversing shaft, and a lever pivotally mounted on said casing and connected to said driven shaft for moving the latter into engagement with said second gear on said reversing shaft. 7

4- An automatic transmission comprising a casing, a driving shaft journaled in said casing, a driven shaft mounted for slight lateral movement in said casing, a pinion on said driven shaft, a sliding gear on said driving shaft, means responsive to the speed of the driving shaft, for controlling the position of said sliding gear on said driving shaft, countershafts in said casing,

transmission gearing on said eountershafts, a train of reversing gears, and means for meshing the pinion on said driven shaft either with said transmission gearing or with said reversing gears.

FABIAN FRIEDMAN. 

